This invention relates to a process of preparing 1,1,1,3,3,3-hexafluoropropane-2-ol by vapor phase catalytic hydrogenolysis of hexafluoroacetone hydrate.
To our knowledge, 1,1,1,3,3,3-hexafluoropropane-2-ol is a compound useful as either a surface active agent or an emulsifying agent (according to Belgian Pat. No. 634,368), as a solvent for some polymers such as vinyl polymers of carboxylic acids (according to U.S. Pat. No. 3,153,004) and also as an intermediate of some anesthetic compounds (according to U.S. Pat. No. 3,346,448).
Usually 1,1,1,3,3,3-hexafluoropropane-2-ol is prepared from hexafluoroacetone, and various kinds of reduction of hydrogenation methods for this purpose have heretofore been proposed. Typical examples of such proposals are liquid phase reduction of hexafluoroacetone using sodium boron hydride as catalyst as represented by U.S.S.R Pat. No. 138,604, liquid phase hydrogenation of hexafluoroacetone using a platinum oxide catalyst as represented by U.S. Pat. No. 3,607,952, and vapor phase catalytic hydrogenation of hexafluoroacetone using a palladium catalyst which may be carried on carbon or alumina as represented by German Pat. No. 1,956,629.
Hexafluoroacetone as the starting material common among the above described known processes is a compound gaseous at room temperature. Accordingly in industrial practice of any of these processes care must be taken in storing, handling and transporting hexafluoroacetone. Moreover, it is very difficult and uneconomical to extremely purify gaseous hexafluoroacetone as an industrial material, and therefore it is inevitable that gaseous hexafluoroacetone for use in the aforementioned catalytic hydrogenation processes contains small or trace amounts of impurities such as hydrogen chloride, hydrogen fluoride and chloropentafluoroacetone. The presence of such impurities becomes a matter of serious disadvantage in industrial preparation of 1,1,1,3,3,3-hexafluoropropane-2-ol by any of the known catalytic hydrogenation processes because the impurities cause significant and rapid poisoning or deactivation of the catalyst.